Shared Bootstrap Capacitor for Multiple Phase Buck Converter Circuit and Methods

• US 20160043624A1
• Filed: 08/11/2014
• Published: 02/11/2016
• Est. Priority Date: 08/11/2014
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Routama, Jarkko Antero, Jarvinen, Jere Andreas Mikael
• Granted Patent: US 9,419,509 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02M 1/084 using a control circuit common to several phases of a multi-phase system
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 3/1586 switched with a phase shift, i.e. interleaved
• CPC Class Codes: H03K 17/00 Electronic switching or gating, i.e. not by contact-making and –breaking gated amplifiers H03F3/72; switching arrangements for exchange systems using static devices H04Q3/52

Abstract

A multiple phase dc to dc converter with a shared bootstrap capacitor. In an embodiment, a multiple phase buck converter is disclosed including a plurality of n switching stages, each coupled to a corresponding switching node, each further including a high side driver MOS device coupled between a terminal for a positive voltage supply terminal and the corresponding switching node; and an inductor coupled in parallel between the corresponding switching node and an output terminal configured for providing the DC output voltage; and high side driver control circuitry configured to selectively couple a shared bootstrap capacitor to a gate terminal of each of the high side drivers, wherein the shared bootstrap capacitor is configured to charge a gate capacitance of each of the high side driver MOS devices. Additional embodiments are disclosed.

Claims

1. A buck converter for producing a DC output voltage from a DC input voltage, comprising:

a plurality of n switching stages, each coupled to a corresponding switching node, each of the n switching stages further comprising;

a high side MOS switch coupled between an input terminal for a positive input voltage and the corresponding switching node;

an inductor corresponding to each of the n switching stages coupled in parallel between the corresponding switching node and an output terminal and configured for providing the DC output voltage; and

high side driver circuitry configured to selectively couple a shared bootstrap capacitor to a gate terminal of a respective one of the high side MOS switches within each of the n switching stages, wherein the bootstrap capacitor is configured to charge a gate capacitance of the respective one of the high side MOS switches.

2. The buck converter of claim 1, wherein n is an integer equal to two.

3. The buck converter of claim 1 wherein n is an integer greater than or equal to two.

4. The buck converter of claim 1, wherein the high side MOS switch in each of the n switching stages is an N-type MOS transistor.

5. The buck converter of claim 1, and further comprising bootstrap capacitor charging circuitry configured to selectively couple a top plate of the shared bootstrap capacitor to a positive supply voltage and to selectively couple a bottom plate of the shared bootstrap capacitor to a ground potential.

6. The buck converter of claim 1, and further comprising the high side driver turn on control circuitry configured to selectively couple a bottom plate of the shared bootstrap capacitor to the input terminal for a positive input voltage and to selectively couple a top plate of the shared bootstrap capacitor to a gate terminal of the high side MOS switch of a selected one of the n switching stages.

7. The buck converter of claim 6 wherein the high side driver circuitry further comprises n high side drivers corresponding to each of the n switching stages and each coupled between a top plate of the shared bootstrap capacitor and a gate terminal of a corresponding one of the high side MOS switches.

8. The buck converter of claim 7 wherein the high side drivers each further comprise a pair of back to back N-MOS transistors series coupled between the top plate of the shared bootstrap capacitor and the gate terminal of a corresponding one of the high side MOS switches, the back to back N MOS transistors having a shared gate terminal coupled to the high side driver turn on control circuitry.

9. An integrated circuit configured to provide a DC to DC voltage converter in a buck configuration, comprising:

a plurality of n switching stages having n switching node outputs, each of the plurality of n switching stages further comprising;

a high side N MOS switch device having a gate terminal and being coupled between a positive input voltage terminal and a corresponding switching node output;

a low side N MOS switch device having a gate terminal and being coupled between the corresponding switching node output and a ground terminal;

a high side driver that selectively couples a top plate of a bootstrap capacitor to the gate terminal of the high side N MOS switch device responsive to a control input; and

high side driver control circuitry coupled to the control input of the high side driver of each of the n switching stages;

whereby the bootstrap capacitor is shared between the n switching stages.

10. The integrated circuit of claim 9 and further comprising:

bootstrap charging circuitry selectively coupled to the bootstrap capacitor and configured to selectively couple the top plate of the bootstrap capacitor to a positive supply voltage and to selectively couple a bottom plate of the bootstrap capacitor to a ground potential.

11. The integrated circuit of claim 9, wherein the high side driver control circuitry is configured to selectively couple the top plate of the bootstrap capacitor to the high side driver of a selected one of the n switching stages and to selectively couple a bottom plate of the bootstrap capacitor to the positive input voltage terminal.

12. The integrated circuit of claim 9, wherein each of the high side drivers in the n switching stages further comprises a pair of N MOS transistors series coupled back to back, and the pair of N MOS transistors has a common gate terminal coupled to the control input.

13. The integrated circuit of claim 9 wherein n is equal to two.

14. The integrated circuit of claim 9 wherein n is greater than or equal to two.

15. The integrated circuit of claim 9 and further comprising n inductors, each coupled to a corresponding one of the n switching outputs, the n inductors coupled in parallel between the n switching nodes and a voltage output node to form a DC voltage output terminal for a buck converter.

19. The integrated circuit of claim 9, wherein the n switching stages and the shared bootstrap capacitor are provided on a single integrated circuit.

20. The integrated circuit of claim 9, wherein the n switching stages are provided on a single integrated circuit and the shared bootstrap capacitor is provided as an external component coupled to the integrated circuit.

16. A method, comprising:

charging a shared bootstrap capacitor by coupling a top plate of the shared bootstrap capacitor to a positive voltage supply while coupling a bottom plate of the shared bootstrap capacitor to a ground potential; and

subsequently coupling the bottom plate of the shared bootstrap capacitor to the input voltage while simultaneously coupling the top plate of the shared bootstrap capacitor to a gate terminal of a high side N MOS switch within a selected one of n switching stages, so as to provide a bootstrapped voltage greater than the input voltage on the gate terminal of the high side N MOS switch within the selected one of the n switching stages and thereby turn on the high side N MOS switch.

17. The method of claim 16 and further comprising:

decoupling the shared bootstrap capacitor from the selected one of the n switching stages;

subsequently recharging the shared bootstrap capacitor by again coupling a top plate of the bootstrap capacitor to the positive voltage supply while coupling a bottom plate of the bootstrap capacitor to a ground potential; and

subsequently coupling the bottom plate of the shared bootstrap capacitor to the input voltage while simultaneously coupling the top plate of the bootstrap capacitor to a gate terminal of another one of the high side N MOS switches within another selected one of the n switching stages, to provide a voltage greater than the input voltage on the gate terminal and so turn on the high side N MOS switch within the another selected one of the n switching stages; and

subsequently repeating the three above recited steps until each of the n switching stages has been coupled to the shared bootstrap capacitor while it is charged.

18. The method of claim 16, wherein subsequently coupling the bottom plate of the bootstrap capacitor to the input voltage y while simultaneously coupling the top plate of the bootstrap capacitor to a gate terminal of a selected one of the high side N MOS switch further comprises:

coupling a pair of back to back series coupled N MOS transistors between the top plate of the shared bootstrap capacitor and the gate terminal of the high side N MOS switch for the selected one of the n switching stages, and operating the pair of back to back series coupled N MOS transistors by placing a voltage greater than a predetermined gate threshold voltage at a common gate terminal of the pair of back to back series coupled N MOS transistors, so as to turn on the pair of back to back series coupled N MOS transistors.